Formed photovoltaic module busbars

ABSTRACT

A method and apparatus directed to busbar components for photovoltaic modules.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/877,785, filed on Oct. 7, 2015, which is a continuation of U.S.patent application Ser. No. 11/543,440, filed on Oct. 3, 2006, now U.S.Pat. No. 9,184,327, issued on Nov. 10, 2015, the entire contents ofwhich are hereby incorporated by reference herein.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under ZAX-4-33628-05awarded by the United States Department of Energy under the photovoltaic(PV) Manufacturing Research and Development (R&D) Program, which isadministered by the National Renewable Energy Laboratory. The Governmenthas certain rights in the invention.

TECHNICAL FIELD

This invention relates to the field of photovoltaic modules and, inparticular, to busbar components for photovoltaic modules.

BACKGROUND

Photovoltaic (PV) cells provide a renewable source of electrical energy.When PV cells are combined in an array such as in a PV module, theelectrical energy collected from all of the PV cells can be combined inseries and parallel arrangements to provide power with a certain voltageand current. Many recent design and engineering advances have increasedthe efficiency and functionality of PV modules.

One area of development focuses on collecting the electrical energy fromall of the PV cells in a PV module so that the collected electricalenergy can be efficiently transferred to an electrical load connected tothe PV system. For example, SunPower Corporation of San Jose, Calif.,offers a highly efficient solar cell design which locates the metalcontacts needed to collect and conduct electricity on the back surfaceof the PV cells so that cell interconnections do not block incidentsunlight.

Another area of development relates to wiring techniques which mightlower the manufacturing cost of PV module components and facilitate abetter design layout of such components on the PV module. FIG. 1illustrates a conventional busbar 10 for a PV module. The illustratedconventional busbar 10 includes an interconnect bus 12, a plurality ofindividual bus tabs 14, and a linear terminal bus 16. Different busbardesigns may implement fewer or more bus tabs 14 than shown. Theindividual bus tabs 14 are typically soldered or welded to theinterconnect bus 12 at corresponding solder or welding joints 18. Thelinear terminal bus 16 is soldered to the interconnect bus 12 at asimilar solder or welding joint 18. The bus tabs 14 connects toelectrical contacts or ribbons for each row of PV cells, and theterminal bus 16 connects the interconnect bus 12 to a junction box onthe PV module.

FIG. 2 illustrates another conventional busbar 30 for a PV module havingback contact cells. The conventional busbar 30 of FIG. 2 is similar tothe conventional busbar 10 of FIG. 1, except that the conventionalbusbar 30 does not have a terminal bus 16. These types of conventionalbusbars 30 are typically used to connect adjacent rows of PV cells toone another. Other types of cell interconnects are used to connectindividual PV cells to one another within the rows of PV cells.

Wire flattening is another conventional technology to form busbars. Wireflattening employs a bending machine to bend wire into a specified shapeand then a flattening machine to flatten the shaped wire into aflattened sheet having a shape corresponding to the shaped wire.

Some conventional busbars suffer from several disadvantages. Forexample, the use of linear components in conventional busbars results inrelatively long electrical path lengths and, hence, increased voltagedrop between the rows of PV cells and the junction box.

Also, the design and layout of conventional busbars is typically limitedby the availability of conductive ribbons. If multiple ribbon sizes areused, then the inventory costs of purchasing, storing, and handling thevarious ribbon sizes are increased. On the other hand, if only oneribbon size is used, the design and layout of the conductive paths islimited by the physical characteristics (e.g., width, thickness, etc.)of the available ribbon.

Conventional busbars also implement several solder or welding joints foreach busbar (e.g., seven joints for the conventional busbar 30 of FIG.1). These joints are sources of potential physical failure of thebusbar. The thickness of these joints also creates stress on thecorresponding PV cells, which can break and become useless. For example,the joints can add extra stress on the PV cells during modulemanufacturing, and the PV cells can crack, which degrades cellperformance. Such breakage is frequently at the edges of PV cellsbecause the linear configuration of conventional busbars results in aportion of the conventional busbar extending beyond the edge of thetypically cropped corners of the PV cells. Additionally, the cost ofassembly of conventional busbars is relatively high because thefabrication process implements multiple solder or welding joints foreach conventional busbar.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1 illustrates a conventional busbar for a photovoltaic module.

FIG. 2 illustrates another conventional busbar for a photovoltaic modulehaving back contact cells.

FIG. 3 illustrates one embodiment of a formed busbar for a photovoltaicmodule.

FIG. 4 illustrates a more detailed embodiment of the cell connectionpiece of FIG. 3.

FIG. 5 illustrates a more detailed embodiment of the terminal connectionpiece of FIG. 3.

FIG. 6 illustrates another embodiment of a formed busbar for aphotovoltaic module.

FIG. 7 illustrates one embodiment of a pattern of nested busbarcomponents for photovoltaic modules.

FIG. 8 illustrates another embodiment of a pattern of nested busbarcomponents for photovoltaic modules.

FIG. 9 illustrates one embodiment of a photovoltaic module with aplurality of formed busbars.

FIG. 10 illustrates one embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 11 illustrates another embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 12 illustrates another embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 13 illustrates another embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 14 illustrates another embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 15 illustrates one embodiment of an angled terminal bus.

FIG. 16 illustrates another embodiment of a manufacturing pattern for aplurality of formed busbar components for photovoltaic modules.

FIG. 17 illustrates another embodiment of a formed cell connection piecehaving an expansion joint.

FIG. 18 illustrates one embodiment of an electrical insulator between abusbar and a back contact cell.

FIG. 19 illustrates a flow chart diagram of one embodiment of afabrication method for using formed busbars to fabricate a photovoltaicmodule.

DETAILED DESCRIPTION

The following description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent invention. It will be apparent to one skilled in the art,however, that at least some embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the spirit and scope ofthe present invention.

In general, this disclosure relates to unitarily formed busbarcomponents for photovoltaic (PV) modules. The term “elements” is used todescribe unitary features of a unitarily formed busbar component. Incontrast, the present application uses the terms “pieces” and “parts” torefer to non-unitarily formed components. Thus, a conventional,non-unitarily formed busbar component has separate pieces.

In one embodiment, a method includes providing a sheet of conductivematerial, and forming a photovoltaic module busbar component from thesheet of conductive material. In some embodiments, the busbar componentmay be a cell connection piece having an interconnect bus and aplurality of unitarily formed bus tabs. In some embodiments, the busbarcomponent may be a terminal bus having a nonlinear portion. Otherembodiments of the method are also described.

In one embodiment, a cell connection piece includes an interconnect busand a plurality of bus tabs. The plurality of bus tabs are unitarilyformed with the interconnect bus and extend away from the interconnectbus. In some embodiments, the cell connection piece is used to connectto a row of PV cells. In some embodiments, the interconnect bus has acontinuously variable width along a length of the interconnect bus.Alternatively, the interconnect bus may have a step-wise variable widthalong a length of the interconnect bus.

In some embodiments, the interconnect bus includes an extension, at anend of the interconnect bus, to provide a solder location to solder aterminal bus to the interconnect bus, although other types of couplingother than solder may be implemented. In some embodiments theinterconnect bus includes one or more expansion joints to accommodatethermal expansion of the PV module because the PV module may have adifferent thermal expansion coefficient than the interconnect bus. Insome embodiments, the interconnect bus includes a plurality of notchesto accommodate a second plurality of bus tabs of a second cellconnection piece in a fabrication process of the cell connection pieces.This implementation facilitates increased material utilization in thepattern layout when stamping the cell connection pieces. Otherembodiments of the cell connection piece are also described.

In one embodiment, a terminal bus includes a terminal connection end, acell connection end, and a nonlinear portion. The terminal connectionend may be used to couple the terminal bus to an electrical terminal ofa junction box. The cell connection end is opposite the terminalconnection end and may be used to connect the terminal bus to a cellconnection piece or, alternatively, directly to one or more photovoltaiccells. The nonlinear portion is between the terminal connection end andthe cell connection end. Other embodiments of the terminal bus are alsodescribed.

In one embodiment, an apparatus includes means for coupling aphotovoltaic cell of a photovoltaic module to a junction box of thephotovoltaic module, and means for reducing a number of coupling jointsbetween the photovoltaic cell and the junction box. In anotherembodiment, an apparatus includes means for coupling a photovoltaic cellof a photovoltaic module to a junction box of the photovoltaic module,and means for providing a curvilinear electrical pathway between thephotovoltaic cell and the junction box. Other embodiments of theapparatus are also described.

FIG. 3 illustrates one embodiment of a formed busbar 100 for aphotovoltaic (PV) module. The depicted formed busbar 100 includes twoformed busbar components: a cell connection piece 102 and a terminalconnection piece 104. The cell connection piece 102 facilitateselectrical connection at one or more PV cells within the PV module. Oneexample of a cell connection piece 102 is shown and described in moredetail with reference to FIG. 4. The terminal connection piece 104facilitates electrical connection between the cell connection piece 102and a junction box of the PV module. One example of the terminalconnection piece 104 is shown and described in more detail withreference to FIG. 5. In one embodiment, a solder joint 106 may be usedto couple the terminal connection piece 104 to the cell connection piece102. For convenience, the description provided herein refers tosoldering, in many instances. However, alternative joining technologiessuch as welding, electrically conductive adhesives, mechanicalfasteners, or other coupling technologies may be implemented.

In another embodiment, the cell connection piece 102 and the terminalconnection piece 104 may be formed as a single, unitary piece. Formingthe cell connection piece 102 and the terminal connection piece 104 as asingle, unitary piece would alleviate the need for a coupling joint suchas the solder joint 106.

FIG. 4 illustrates a more detailed embodiment of the cell connectionpiece 102 of FIG. 3. The depicted cell connection piece 102 includes aninterconnect bus 108 and multiple bus tabs 110. In one embodiment, thecell connection piece 102 may include three bus tabs 110 for connectionsto each of the corresponding PV cells. Alternatively, the cellconnection piece 102 may include two bus tabs 110, or more than threebus tabs 110, for each corresponding PV cell.

As depicted in FIG. 4, the bus tabs 110 are unitarily formed with theinterconnect bus 108 such that coupling joints are not necessary tocouple the bus tabs 110 to the interconnect bus 108. By implementing aunitarily formed cell connection piece 102 without coupling joints, thecell connection piece 102 may have increased mechanical strength andreliability compared to conventional busbar components which usecoupling joints. Additionally, the thickness of formed busbar componentsmay be significantly less than the thickness of conventional busbarcomponents which use coupling joints. For example, a conventional busbarcomponent with coupling joints may have a total thickness of about 635μm (25 mils) (e.g., 127 μm (5 mils) for the first ribbon layer, 101.6 μm(4 mils) for the solder joint, and 254 μm (10 mils) for the secondribbon layer), but a unitarily formed busbar component may have a totalthickness of about 127 μm (5 mils)—the thickness of a single metallayer. While the exact thickness of a formed busbar component depends atleast in part on the thickness of the metal or other conductive materialused, the overall thickness of the formed busbar component is generallysubstantially less than the overall thickness of a conventional busbarcomponent with solder joints.

In some embodiments, the interconnect bus 108 or the bus tabs 110, orboth, may include non-linear portions. For example, the interconnect bus108 may have a curved shape along the length of the interconnect bus108. Moreover, the interconnect bus 108 and the bus tabs 110 mayintersect at an angle that is not rectilinear. For example, some or allof the individual bus tabs 110 may extend away from the interconnect busat an angle other than 90 degrees (e.g., 60 degrees). In anotherexample, a bus tab 110 at the end of the interconnect bus 108 may beformed as a curvilinear extension of the interconnect bus 108, so thatthe interconnect bus 108 curves approximately 90 degrees to form the bustab 110. With the benefit of this disclosure, various combinations ofrectilinear and curvilinear configurations may be implemented. Forexample, the bus tabs 110 may have rounded ends and rounded interior orexterior corners where the bus tabs 110 intersect the interconnect bus108.

The depicted cell connection piece 102 also includes an extension 112 atone end of the interconnect bus 108. Alternatively, the extension 112may be located at an intermediate position on the interconnect bus 108,instead of at one of the ends. In other embodiments, the cell connectionpiece 102 may omit the extension 112. Where the cell connection piece102 includes an extension, the extension 112 may provide a moredesirable location for the solder joint 106. Where the cell connectionpiece 102 omits an extension, the solder joint 106 may be located atanother position along the length of the interconnect bus 108.

FIG. 5 illustrates a more detailed embodiment of the terminal connectionpiece 104 of FIG. 3. The depicted terminal connection piece 104 is aterminal bus. Although the terminal connection piece 104 is a singlepiece, and does not necessarily include multiple identified pieces,other embodiments of the terminal connection piece 104 may includemultiple identified elements formed in a unitary manner, as describedabove with references to the cell connection piece 102.

Although both the depicted terminal connection piece 104, or terminalbus, and conventional terminal buses are both single pieces which may becoupled to a corresponding interconnect bus, the depicted terminal bus104 is different from conventional terminal buses. In one embodiment,the terminal bus 104 includes a non-linear portion 114. The non-linearportion 114 may implement a curvilinear, angular, or other type ofnon-linear path between the cell connection end and the terminalconnection end of the terminal bus 104. Although the non-linear portion114 is shown primarily at the cell connection end of the terminal bus104 in FIG. 5, other embodiments may implement one or more non-linearportions 114 at other locations of the terminal bus 104.

The non-linear portion 114 may facilitate one or more advantages overconventional, linear terminal buses. In one embodiment, the location ofthe non-linear portion 114 of the terminal bus 104 may be designed toavoid an overlap with an edge of a corresponding PV cell. Whileconventional, linear terminal buses often extend across one or moreedges of a PV cell, causing stress on the PV cell and resulting indamage (e.g., cracking or breakage) of the PV cell, the non-linearportion 114 of the illustrated terminal bus 114 may avoid causingmechanical stress at the edge of corresponding PV cells. Thus, theintegrity of the PV cells and the PV module, as a whole, may bepreserved.

Additionally, the non-linear portion 114 of the terminal bus 104 mayprovide a shorter electrical path between the cell connection piece 102and the junction box of the PV module. Given that voltage drop isrelated to the length of the electrical path between the PV cells andthe junction box, implementing a relatively shorter electrical path mayresult in greater power output from the PV module because less power isconsumed in voltage drop. While the increased power output due todecreased voltage drop of a single PV module may seem trivial, the totalincrease in power output from an array of hundreds or thousands of PVmodules may be significant.

The depicted terminal bus 104 also includes a tapered portion 116 at thejunction connection end of the terminal bus 104. In one embodiment, thetapered portion 116 facilitates coupling the terminal bus 104 to aterminal within the junction box of the PV module. For example, where asmall junction box is used, the tapered portion 116 of the terminal bus104 may allow the terminal bus 104 to connect to the terminal in thejunction box. In contrast, where a non-tapered terminal bus is used, asmall junction box might be too small to accommodate the non-taperedwidth of multiple terminal buses 104.

FIG. 6 illustrates another embodiment of a unitarily formed busbar 120for a PV module. The depicted formed busbar 120 includes a cellconnection piece 122 and a terminal connection piece 124. For purposesof this description, the cell connection piece 122 is substantiallysimilar to the cell connection piece 102 of FIG. 4. However, the cellconnection piece 122 is used to connect to a single PV cell, rather thanto multiple PV cells. Likewise, the terminal connection piece 124 issubstantially similar to the terminal connection piece 104 of FIG. 5,including non-linear portions 128 and 130, as well as a tapered portion132. However, the terminal connection piece 124 includes multiplenon-linear portions 128 and 130 to accommodate a different path from thecell connection piece 122 to a junction box. In particular, the terminalconnection piece 124 may facilitate electrical connection to a PV cellwhich is located a greater distance from the junction box.

FIG. 7 illustrates one embodiment of a pattern 140 of nested busbarcomponents 142 for PV modules. In particular, the illustrated busbarcomponents 142 are terminal buses 104, although other patterns mayaccommodate other types of busbar components. In one embodiment, thepattern 140 of nested terminal buses 104 facilitates stamping, orotherwise unitarily forming, a plurality of individual terminal buses104 from a sheet of conductive material 144. Exemplary conductivematerials that may be used include annealed copper with tin, tin-silver,tin-lead, or tin-silver-copper coating, or other electrically conductivematerials. For convenience, the description provided herein refers tostamping, in many instances. However, alternative forming technologiessuch as electrical discharge machining (EDM), water jet cutting, lasercutting (e.g., in a stack), or other forming technologies may beimplemented.

Stamping employs a die to cut through a sheet of material. The face ofthe die includes a pattern that is forced by a heavy duty press to cutthrough the sheet of material. In one embodiment, the pattern may be fora single component. Alternatively, the pattern may be for severalcomponents. For example, the pattern may be for a plurality of similar,nested components, or even for different types of components.Additionally, some stamping mechanisms may include dies that are capableof stamping multiple layers of material in a stack at a single time. Inthis way, one stamping operation may produce several sets of patternedcomponents (i.e., one set for each sheet of material in the stack).

EDM employs a recurring electrical arcing discharge between an electrodeand the metal sheet 144. The electrode follows the pattern 140 to createa series of micro-craters on the metal sheet 144 and to remove materialalong the cutting path by melting and vaporization. The removedparticles are washed away by a dielectric fluid.

Water jet cutting employs a stream of high pressure of water, with orwithout abrasive additives, through a nozzle to essentially erode themetal sheet 144 along the pattern 140. The nozzle and stream of waterfollow the pattern 140 to cut the individual busbar components 142 outof the metal sheet 144.

Laser cutting, like water jet cutting, cuts the pattern 140 of busbarcomponents 142 out of the metal sheet 144. However, laser cuttingemploys a high power laser, instead of a high pressure stream of water.The part of the metal sheet 144 exposed to the laser melts, burns, orvaporizes. Laser cutting can produce a high quality finish on the cutsurface. Laser cutting, as well as EDM and water jet cutting, may beemployed to cut several sheets 144 at once in a stack.

FIG. 8 illustrates another embodiment of a pattern 150 of nested busbarcomponents 152 for PV modules. In particular, the illustrated busbarcomponents 152 are terminal buses 124, as shown in FIG. 6. In oneembodiment, the pattern 150 facilitates substantial material utilizationbetween the individual busbar components 152. For example, the shape ofthe nested busbar components 152 may use all or almost all of theconductive sheet 154 between the nested busbar components 152.

FIG. 9 illustrates one embodiment of a photovoltaic (PV) module 180 witha plurality of formed busbars 100 and 120. In particular, FIG. 9 showsthe back side of the PV module 180, which is not typically seen from theoutside of the PV module 180. The depicted PV module 180 includes anarray (e.g., a 6×8 array) of PV cells 182. The PV cells 182 are showndashed to indicate that they are located on the front of the PV module180, rather than on the back. At one end of each column of cells 182,formed busbars 100 and 120 couple the columns of cells 182 to a junctionbox 184 coupled to the PV module 180. At the opposite end of each columnof cells 182, formed cell connection pieces 102 couple pairs of columnstogether. In one embodiment, the shape of the cell connection piece 102is universal in that it may be used at either end of the columns ofcells 182. Implementing a universal cell connection piece 102 in thismanner may eliminate the need to fabricate, store, and inventory anadditional number of different types of busbar components. FIG. 9 alsoillustrates that the busbar components may be located behind the PVcells 182 to improve the aesthetic look and electrical efficiency of thePV module 180.

FIG. 10 illustrates one embodiment of a manufacturing pattern 200 for aplurality of unitarily formed busbar components 122 for PV modules. Thedepicted manufacturing pattern 200 orients multiple cell connectionpieces 122 in an opposing and offset orientation. In particular, the bustabs 110 of each cell connection piece 122 are directed to theinterconnect bus 108 of the opposing cell connection piece 122, and someof the bus tabs 110 of each cell connection piece 122 are locatedbetween the bus tabs 110 of the opposing cell connection piece 122. Theorientation of the opposing cell connection pieces 122 in thismanufacturing pattern 200 may reduce the amount of unutilized materialbetween the opposing cell connection pieces 122. By orienting the pairsof cell connection pieces 122 in a back-to-back pattern on a conductivesheet 124, as shown, the material utilization between the pairs of cellconnection pieces 122 can be very high (the unused material is indicatedwith cross-hatching).

FIG. 11 illustrates another embodiment of a manufacturing pattern 210for a plurality of unitarily formed busbar components 212 for PVmodules. The depicted cell connection pieces 212 are similar to the cellconnection pieces 122, except that the cell connection pieces 212 haveinterconnect buses 108 with a continuously variable width along thelength of each interconnect bus 108. Implementing the cell connectionpieces 212 may reduce the amount of material for each cell connectionpiece 212 according to the reduced width of the interconnect bus 108. Inone embodiment, the pairs of cell connection pieces 212 are arranged ona conductive sheet 214 in a side-to-side pattern, as shown.Alternatively, adjacent pairs of cell connection pieces 212 may bearranged in a back-to-back pattern as shown in FIG. 10, so that thetapered edge of one cell connection piece 212 may coordinate with thetapered edge of another cell connection piece 212 (e.g., a third cellconnection piece 212) to eliminate material waste between adjacent setsof cell connection pieces 212 (the unused material is indicated withcross-hatching).

FIG. 12 illustrates another embodiment of a manufacturing pattern 220for a plurality of unitarily formed busbar components 222 for PVmodules. The depicted cell connection pieces 222 are similar to the cellconnection pieces 122, except that the cell connection pieces 222 haveinterconnect buses 108 with notches to allow the bus tabs 110 of theopposite cell connection piece 222 to extend into the notches. Byallowing the bus tabs 110 of the opposing cell connection pieces 222 toextend into the notches in the corresponding interconnect buses 108, thecombined area of the manufacturing pattern 220 may be reduced comparedto the combined area of the manufacturing pattern 200 of FIG. 10(without the notches). In other words, there may be less unutilizedmaterial between the opposing cell connection pieces 222 of FIG. 12.

FIG. 13 illustrates another embodiment of a manufacturing pattern 230for a plurality of unitarily formed busbar components 232 for PVmodules. The depicted cell connection pieces 232 are similar to the cellconnection pieces 222, except that the cell connection pieces 232 haveinterconnect buses 108 with a continuously variable width along thelength of the interconnect bus 108. As described above with reference tothe cell connection pieces 212 of FIG. 11, implementing the cellconnection pieces 232 with tapered edges may reduce the amount ofunutilized material for each cell connection piece 232 according to thereduced width of the interconnect bus 108.

FIG. 14 illustrates another embodiment of a manufacturing pattern 240for a plurality of unitarily formed busbar components 242 for PVmodules. The depicted cell connection pieces 242 are similar to the cellconnection pieces 232 of FIG. 13, except that the cell connection pieces242 have interconnect buses 108 with a step-wise variable width alongthe length of the interconnect bus 108. In one embodiment, the step-wisevariable width of the interconnect bus 108 may reduce the amount ofmaterial used for the cell connection piece 242. In some embodiments,the step-wise variable edge of the interconnect bus 108 may coordinatewith the step-wise variable edge of another cell connection piece 242(e.g., a third cell connection piece 242) to eliminate material wastebetween adjacent sets of cell connection pairs (because the sets of cellconnection pairs are aligned at the step-wise variable edges of theinterconnect buses 108).

FIG. 15 illustrates one embodiment of an angled terminal bus 250. Theangled terminal bus 250 is another example of a non-linear terminalconnection piece, as described above. The depicted angled terminal bus250 includes two linear portions 252 and 254 connected by a non-zeroangled portion 256. Similar to the non-linear portion 114 of theterminal connection piece 104 of FIG. 5, the angled portion 256 of theterminal bus 250 may be designed to avoid an overlap with an edge of acorresponding PV cell 182. Additionally, the angled portion 256 of theterminal bus 250 may provide a relatively shorter electrical pathbetween a corresponding cell connection piece 102 and the junction box184 of the PV module 180.

The depicted angled terminal bus 250 also includes a unitarily stampedhole 258. Alternatively, the hole 258 may be formed in another mannerconsistent with the formation technology used to form the angledterminal bus 250. In one embodiment, the hole 258 is used to allow afastener within the junction box 184 to secure the terminal bus 250 toan electrical terminal (not shown) within the junction box 184. Forexample, a screw may be used to fasten the terminal bus 250 to theelectrical terminal, although other types of fasteners may be used inother embodiments.

FIG. 16 illustrates another embodiment of a manufacturing pattern 270for a plurality of unitarily formed busbar components 272 for PVmodules. The depicted cell connection pieces 272 are similar to the cellconnection pieces 122 of FIG. 10, except that the cell connection pieces272 have more bus tabs 110 and the interconnect buses 108 have asymmetrically variable width along the length of the interconnect bus108. In one embodiment, the symmetrically variable width of theinterconnect bus 108 may reduce the amount of material used for the cellconnection piece 272. In some embodiments, the symmetrically variablewidth of the interconnect bus 108 may coordinate with the symmetricallyvariable edge of one or more other cell connection piece 272 toeliminate material waste between adjacent sets of cell connection pairs.Additionally, the symmetrically variable width of the interconnect bus108 may provide a convenient location for a central solder joint atabout the widest portion of the interconnect bus 108. In furtherembodiments, the cell connection pieces 272 may be used forstring-to-string connection without a terminal bus (similar to the cellconnection pieces 102 at the bottom of FIG. 9). Also, the sloping of theinterconnect bus 108 may be designed to be consistent with the amount ofcurrent that may be needed to be carried in the bus.

FIG. 17 illustrates another embodiment of a unitary cell connectionpiece 280 having an expansion joint 282. The use of an expansion joint282 may accommodate thermal expansion of the various parts of the PVmodule 180, since the PV cells 182 and PV module 180 likely have adifferent thermal coefficient of expansion than the conductive materialused for the busbar components. In this way, the expansion joint 282lowers stress, thereby improving reliability. Although the expansionjoint 282 is shown in a particular location between two groups of bustabs 110, the expansion joint 282 may be located at another locationalong the interconnect bus 108. Additionally, a busbar component mayinclude multiple expansion joints 282. In some embodiments, terminalconnection pieces 104 also may include similar expansion joints. Theexpansion joints 282 may be formed in a variety of ways, includingcrimping or otherwise bending the interconnect bus 108. In oneembodiment, the expansion joint may be formed during a stamping process.Alternatively, the expansion joint may be formed in another manner.

FIG. 18 illustrates a side view of one embodiment of a busbar 100coupled to a back contact cell 182. In particular, the busbar 100 iscoupled to the back contact 292 on the back side of the cell 182. Inorder to prevent the busbar 100 from contacting any electricalcomponents on the back of the cell 182, an electrical insulator material294 is provided between the busbar 100 and the back of the cell 182. Alaminate material 296 is provided to cover the busbar 100 and insulatormaterial 294.

In one embodiment, the electrical insulator material 294 is EPE(EVA/polyester/EVA) made from 101.6 μm (4 mils) ethylene vinyl acetate(EVA), 50.8 μm (2 mils) polyester, and 101.6 μm (4 mils) EVA.Alternatively, other insulator materials may be used. In someembodiments, the insulator material 294 may be applied to the busbar100. In some embodiments, the insulator material 294 may be made to havea certain color (e.g., white or black). Alternatively, the insulatormaterial 294 may be transparent. In embodiments where the busbar 100 isnot adjacent to the cell 182, the insulator material 294 may be omitted.

For PV modules 180 which use electrical ribbons instead of backcontacts, the busbars 100 may couple to the electrical ribbon. Where theribbons are provided on the front of the cell 182, the ribbons may befolded over behind a cell 182 for connection to the busbar 100.Alternatively, the ribbons may extend past the cell 182 and the busbarmay be located away from the cell 182, rather than behind the cell 182.Other embodiments may implement other configurations.

FIG. 19 illustrates a flow chart diagram of one embodiment of afabrication method 300 for using unitarily formed busbars 100 tofabricate a PV module 180. Alternatively, other embodiments of thefabrication method 300 may include additional operations or feweroperations than are shown and described herein.

The depicted fabrication method 300 begins as unitarily formed, nestedbusbar components are stamped 305 from a metal sheet or other conductivematerial. In one embodiment, the busbar components include cellconnection pieces 102 or terminal connection pieces 104, or both.Subsequently, individual formed busbar components such as a cellconnection piece 102 and a terminal connection piece 104 are arranged310 on a PV module 180. The busbar components are then soldered 315together and coupled to the cell contacts or cell ribbons. In oneembodiment, heat insulators (not shown) may be used to provideinsulation for the PV cells 182 against the heat and pressure generatedat the solder joint 106 to couple the cell connection piece 102 and theterminal connection piece 104. The busbar components are then connected320 to the junction box 184. In particular, the terminal bus 104 may besecured to an electrical terminal within the junction box 184. Theillustrated fabrication method 300 then ends.

Embodiments of the present invention, described herein, include variousoperations. These operations may be performed manually, automatically,or a combination thereof. Although the operations of the method(s)herein are shown and described in a particular order, the order of theoperations of each method may be altered so that certain operations maybe performed in an inverse order or so that certain operation may beperformed, at least in part, concurrently with other operations. Inanother embodiment, instructions or sub-operations of distinctoperations may be in an intermittent and/or alternating manner.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A photovoltaic (PV) module, the PV modulecomprising: one or more back contact PV cells located within the PVmodule, wherein the one or more back contact PV cells have a front sideand a back side, the front side opposite the back side; a busbarelectrically connected to the back side of the one or more back contactPV cells, wherein the busbar is disposed over the back side of the backcontact PV cell; and an insulator material located between the busbarand the one or more back contact PV cells.
 2. The PV module of claim 1,wherein the insulator material comprises a material selected from thegroup consisting of EPE, polyester and EVA.
 3. The PV module of claim 1,wherein the insulator material comprises a colored insulator material.4. The PV module of claim 1, wherein the insulator material comprises awhite colored insulator material or a black colored insulator material.5. The PV module of claim 1, wherein the insulator material comprises atransparent insulator material.
 6. The PV module of claim 1, wherein theinsulator material has a thickness in a range of 2-4 mils.
 7. The PVmodule of claim 1, further comprising: a laminate material located onthe busbar and one or more back contact PV cells.
 8. The PV module ofclaim 1, wherein the busbar comprises: a cell connection pieceelectrically connected to the one or more back contact PV cells; and aterminal connection piece coupled with the cell connection piece.
 9. ThePV module of claim 8, wherein the cell connection piece is unitarilyformed with the terminal connection piece.
 10. A photovoltaic (PV)module, the PV module comprising: a cell connection piece electricallyconnected to a back side of one or more back contact PV cells; and aterminal connection piece unitarily coupled with the cell connectionpiece to form a unitary connection piece, wherein the unitary connectionpiece is located behind the one or more back contact PV cells.
 11. ThePV module of claim 10, wherein the cell connection piece comprises aplurality of bus tabs extending from a single side of with the cellconnection piece.
 12. The PV module of claim 10, wherein the cellconnection piece comprises an interconnect bus having a continuouslyvariable width along a length of the interconnect bus.
 13. The PV moduleof claim 10, wherein the cell connection piece comprises an interconnectbus having a step-wise variable width along a length of the interconnectbus.
 14. The PV module of claim 10, wherein the cell connection piececomprises an expansion joint to accommodate thermal expansion of thephotovoltaic module, wherein the expansion joint is unitarily formedwith the cell connection piece.
 15. The PV module of claim 10, whereinthe terminal connection piece comprises a terminal bus bar including afirst portion defining a non-orthogonal, curvilinear shape and a secondportion defining either a tapered shape or a hole to facilitate couplingof the second portion of the terminal bus bar to a terminal of ajunction box.
 16. A method for fabricating a photovoltaic (PV) module,the method comprising: arranging busbar components on the PV module;soldering or welding a linear terminal bus of the busbar components toan interconnect bus of the busbar components, wherein insulators provideinsulation from heat at a joint during the soldering or welding; andcoupling the busbar components to the back contact PV cells.
 17. Themethod of claim 16, further comprising: prior to arranging busbarcomponents on the PV module, forming the busbar components from aconductive material.
 18. The method of claim 16, wherein soldering orwelding the linear terminal bus to interconnect bus of the busbarcomponents comprises soldering or welding the linear terminal bus to acorresponding joint of the interconnect bus.
 19. The method of claim 16,further comprising: connecting the busbar components to the junctionbox.
 20. The method of claim 19, wherein connecting the busbarcomponents to the junction box comprises securing the terminal bus to anelectrical terminal of the junction box.